Holding means for laminated relief printing plate



June 11, 1968 E. J. HORNER 3,387,559

HOLDING MEANS FOR LAMINATED RELIEF PRINTING PLATE Filed Aug. 4, 1967/////A /fl// V// INVENTOR. F G. 7 fizz/map baa/5P ATTORNEYS UnitedStates Patent 3,387,559 HOLDING MEANS FOR LAMINATED RELIEF PRINTINGPLATE Ellwood J. Horner, Armonk, N.Y., assignor to R. Hoe &

Co. Inc., New York, N.Y., a corporation of New York Continuation-impartof application Ser. No. 545,770,

Apr. 27, 1966. This application Aug. 4, 1967, Ser.

3 Claims. (Cl. 101-683) ABSTRACT OF THE DISCLOSURE An elongated springhaving a straight leg and a curved leg so as to fit complementallybetween a laminated relief printing plate and an edge of a saddle forholding the plate securely to the saddle. The plate is composed of azinc printing layer to be etched and a supporting layer of aluminum andis curved so as to fit on the saddle by which the plate is mounted on aprinting cylinder.

This application is a continuation-in-part of Homer application Ser. No.545,770 filed Apr. 27, 1966, for Laminated Relief Printing Plate andMeans for Holding Same, now abandoned in favor of application Ser. No.672,929 filed Oct. 4, 1967.

Background of the invention This invention relates to relief printingplates for rotary printing machines and more particularly to a means forsecurely holding such a plate on a saddle.

In rotary relief printing as heretofore practiced the plate hastypically been formed as a casting, as for example, the familiarnewspaper stereotype plate. Such plates are heavy and formed of metal(typically a lead-tin-antimony alloy) which has a low tensile strength.Also the production of the flong requires mechanical composition of theentire subject-matter to be carried by the plate.

To some extent, electrotypes have been used, but the expense is high andthis type of printing surface has been available only for high qualityprinting.

In an effort to simplify the production of the plate, etched plates,typically of zinc, have been used, the plate being either etched in itscurved form or produced flat and then bent to the required curve to fitthe printing cylinder. Even where the plate is comparatively thick, itinevitably distorts due to its variations in thickness when etched andthe difliculty of holding it properly in place due to the plasticity orcreep of the metal.

Relief printing using rubber or synthetic resin printing surfaces hasbeen practiced with some success, but such surfaces hold no promisewhatever of producing plates of comparable durability and sharpness ofprinting to what can be had with metal plates, or at comparable cost.

In Horner application, Ser. No. 454,139 filed Oct. 12, 1965 and nowabandoned for Laminated Relief Printing Plate, there is disclosed azinc-aluminum plate which is substantially free of the deficiencies ofprior proposals.

The object of the present invention is to provide a means for securelyholding such a plate having a composite plate structure to a saddle foradapting the zincaluminum laminated plate to use with printing machinesusing softer surfaced form rollers and impression blankets, and ingreater thickness as to the laminated plate itself.

Brief description of the drawings In the drawings FIG. 1 is an enlargedfragmentary section of a composite plate in the flat and prior toetching which is to be secured to a saddle by the present invention.

FIG. 2 is an isometric view of the present invention.

Patented June 11, 1968 Description of the preferred embodiment of theinvention As explained in the above mentioned application, the variousareas of the relief halftone printing plate are reproduced by et-chingas indicated in FIG. 7. The small highlight dots 1 are formed by etchingthe metal around these dots away as indicated at 1A. The depth of etchof such areas is comparatively great and may be five or six thousandthsof an inch. In the middle tones the printing dots 2 and spaces 2Abetween them are comparable in area and the depth of etch is less thanin the highlights, being three to four thousandths of an inch. In theshade areas the etched away portions 3A are small and isolated and theunetched area 3 occupies the remainder of the surface. The etching depthhere is slight, being from one to three thousandths of an inch. Wheretypographic or other line material is printed, or where there is anonprinting area of the plate, the etching 4A around the line printingelements 4 proceeds to a comparatively great depth, where the etching isdone in a single step. A nitric acid etchant with suitable additionagents is used, so that the walls of the etched out depressions of theplate will be at a substantial constant angle, making the depth of etchproportional to the width of the etched area. Under these circumstances,if a solid zinc plate were used the etching in the line and non-printingareas would go far below the .030" depth specified. However, in thecomposite plate the aluminum backing layer is not affected by theetchant so that its surface defines a limit to the depth of etch. In theplate shown the zinc layer is about .030", while the aluminum supportinglayer is about .020 in thickness.

The increased depth of etch in the non-printing areas, as compared tothe disclosure of the above mentioned application, permits the use ofthe plate with wide, softsurfaced impression cylinders. The increasedthickness of the aluminum layer stiifens up the plate so that it can beclipped over a saddle for attachment to printing cylinders withunderneath tensioning hooks for the plate.

As shown in FIG. 2 with reference to one end of the plate, the plateends are bent first in a 45 degree bend 10 and then back in a degreebend 11 so as to hook over the ends of a supporting saddle.

The plate may be used with any of various saddles which are adapted toholding it in place on a cylinder, as for example, the expandable saddleshown in Faeber Patent 2,966,848. It is preferred, however, to supportthe plate on a rigid saddle which is fitted with spring holding means atone end, such as provided by the present invention.

As shown generally in FIG. 3 the saddle 20 is semicylindrical in form.At each straight end it has a groove 21, for receiving the clampinghooks which hold it to the printing cylinder. The straight ends 22 arebevelled or slanted back under the saddle outer surface at an angle ofabout 45 degrees to the cylinder surface. The plate clips over thesaddle as shown in FIG. 4, the bends 10 fitting around the ends 22 ofthe saddle. At one end there is provided the present inventioncomprising a spring holding means 23 running the length of the end 22.The spring is of a novel construction as shown in FIG. 2, comprising anelongated leaf spring having a U shaped cross section with one leg 25thereof straight and the other leg 26 being curved in an S shapedconfiguration. When the spring is in position between the saddle andplate as shown in FIG. 6 the upper part of the S 27 conforms to and willbe urged against the inner side of the bend it? of the plate so as totension the plate on the saddle. The upper convex part of the S curve isdesigned to fit complementary with the bend 11 of the plate and thelower concave part of the curve continues around into the straight legforming the heel of the spring. This heel portion does not exert aforced against the bend 11 of the plate, if it did the plate would beurged off the saddle. Only the upper portion 27 exerts a force againstthe plate in such a way as to keep the plate held securely on thesaddle.

Preferably the spring is attached to the straight end 22 of the saddle.For this reason the spring is provided with cutouts 24- forming a liphaving holes for receiving screws or bolts which are to be fastened tothe straight end 22 of the saddle, thereby attaching the spring to thestraight end 22.

In attaching the plate, one end It) is hooked over the spring 23 asshown in FIG. 4. At this time the other, or register, end will not be inplace. The spring-held end is now forced against the saddle as shown inFIG. 5, using for this purpose any convenient clamping arrangementfitting in the groove 21. The bend 11 at the opposite end of the platewill now clear the edge 22 so that this end may be snapped into place.The springheld end is now released, permitting the spring 23 to expandslightly (FIG. 6) thus holding the plate down snugly on the saddle.

The weight of the plate may be only about two pounds, for a platemeasuring about 15" along the straight edges 22 or 22 inchescircumferentially. The spring 23 exerting a holding force of about 150lbs. (about lbs. per axial inch of plate) will hold the plate on thesaddle satisfactorily at speeds of 25 thousand cylinder revolutions perhour or higher. Higher spring force may also be used where needed, andit is therefore preferable to make the spring 23 with a potential ofexerting approximately 820 lbs. of force per lineal inch.

The plate itself is bent into cylindrical form (preferably prior toetching) and to a greater curvature than that of the saddle. In theusual size of plate the radius of curvature of the plate may be betweena half inch and one inch less than that of the saddle. Under theseconditions, the plate is made to hug the saddle snugly and the interfacebetween zinc and aluminum layers retains substantially the same lengthas it had in the plate prior to bending.

While it is preferred to bend the plate to its cylindrical form prior toetching, it may also be etched in the fiat, the recessed or depressedareas which are thus formed being suitably packed during bending.

It is essential that the zinc and aluminum layers be of 4 controlled anduniform thickness and that they be molecularly bonded together.Laminations produced according to Boessenkool Patents 2,691,815 and2,753,623 are, as pointed out in the above mentioned application,.satisfactory.

Because of the uniqueness of the composite plate and saddle arrangementsit is essential that the means for holding the plate on the saddle be ofproper design and configuration. It can be seen from the forgoingdescription that the present invention adequately performs the requiredfunction of securely holding the plate to the saddle.

What is claimed is:

1. Printing plate holding means for printing cylinders comprising anetched bi-metallic printing plate for relief half-tone printing, asupporting saddle adapted to be reeasably held on a said cylinder forsupporting said plate, said saddle having its ends slanted back underits outer surface, said plate comprising a printing layer of zinc and abacking layer of aluminum molecularly bonded together, the printinglayer of zinc having a uniform thickness of approximately .03 inch beingparallel to the aluminum backing layer having a uniform thickness ofabout .02 inch, the plate being curved to a smaller radius of curvaturethan the saddle surface and being bent under at its straight ends intoan S curve, the said bent ends fitting over said saddle ends and underthe edges thereof, and an elongated leaf spring fitted on one end ofsaid saddle engaging a said bent end for tensioning the plate onto saidsaddle and holding the other bent end of the plate against the saddle,said spring having a substantially U shaped cross section with one legthereof straight and secured to the saddle end and the other leg curvedin an S configuration conforming to said plate bent end so that thespring fits between the straight end of the saddle and the bent end ofthe plate.

2. The printing plate holding means according to claim 1 wherein saidspring straight leg has cutouts therefrom along its length forming aplurality of lips provided with holes for attaching the spring to thestraight end of the saddle.

3. The printing plate holding means according to claim 2 wherein thespring has a potential of exerting approximately between 8 and 20 lbs.per lineal inch.

References Cited UNITED STATES PATENTS 2,248,275 7/1941 'Lengel 10l3952,257,143 9/1941 Wood 10140l.1 X 2,970,540 2/1961 VVirth 10l4l5.l

ROBERT E. PULFREY, Primary Examiner.

F. A. WINANS, Assistant Examiner.

